Embodiments of the present invention relate to a wind turbine blade.
In particular, embodiments of the present invention relate to a large scale wind turbine blade which is at least 45 meters long from root to tip.
Wind turbine blades of increasing length are desirable as the increase in length of the blade produces a disproportionately high increase in the power output for unit cost. However, the ever increasing length of wind turbine blades produces new technical challenges. To some extent, existing blade technology can simply be scaled up as it is. However, this can only go so far before problems arise.
One particular problem with long wind turbine blades is that of torsional stiffness. Typically, as the blade length increases, inadequate torsional stiffness results in excessive twist of the blade, problems with flutter and other instabilities.
The way that the stiffness has routinely been improved is to increase the amount of glass fibre in the laminate lay-up as the blade is formed. This additional glass fibre is normally placed in the outer aerodynamic structural shell of the blade. This aerodynamic shell forms a “torsion box” which effectively deals with the torsional stability of the blade. The fibre is typically placed in a biaxial arrangement. However, this is not mass or cost effective as a significant amount of glass fibres is required.